Tesi sul tema "Time-Resolved spectroscopie"
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Hawecker, Jacques. "Terahertz time resolved spectroscopy of Intersubband Polaritons and Spintronic Emitters". Electronic Thesis or Diss., Sorbonne université, 2021. http://www.theses.fr/2021SORUS101.
The terahertz (THz) domain provides a rich playground for many practical and fundamental applications, where the low energy of THz photons permits to probe novel light-matter interactions. This work investigates two recent and emerging scientific areas where ultrafast THz spectroscopy can be used as a probe of fundamental phenomena, as well as potentially enabling the conception of new THz sources. In the first case, ultrafast THz spintronics are studied where ultrafast excitations of spintronic heterojunctions result in efficient pulse generation. These structures consist of nanometer thick ferromagnetic - heavy metal junctions, where an optically generated spin-charge in the former is converted to a charge-current in the latter via the Inverse Spin Hall Effect. Beyond these metal-based junctions, ultrafast THz spintronics based on “quantum” materials is also investigated, where THz pulses are generated using quantum phenomena such as the Inverse Edelstein Effect in Topological Insulators, shown to be a promising research direction. The second subject area is focused on THz intersubband polaritons, quasi-particles that emerge from the strong light-matter coupling of a THz photonic cavity and an intersubband transition. Here we are interested in the bosonic nature of the intersubband polaritons, as a long-term aim of realizing a novel THz laser based on Bose-Einstein condensation. In this work, we investigate resonant narrowband pumping of a polariton branch and probe using spectrally broad THz pulses. This shows strong indications of nonlinear effects and potential signatures of scattering processes that could eventually lead to the demonstration of THz polaritonic gain. Finally, to support our work in the above subject areas, technological developments were made in existing THz sources. This included high power THz photoconductive switches using cavities, which permitted the first demonstrations of real time THz imaging with such devices, and high power THz quantum cascade lasers as narrowband laser pumps
Gaury, Benoit. "Emerging concepts in time-resolved quantum nanoelectronics". Thesis, Grenoble, 2014. http://www.theses.fr/2014GRENY026/document.
With the recent technical progress, single electron sources have moved fromtheory to the lab. Conceptually new types of experiments where one probesdirectly the internal quantum dynamics of the devices are within grasp. In thisthesis we develop the analytical and numerical tools for handling suchsituations. The simulations require appropriate spatial resolution for thesystems, and simulated times long enough so that one can probe their internalcharacteristic times. So far the standard theoretical approach used to treatsuch problems numerically---known as Keldysh or NEGF (Non Equilibrium Green'sFunctions) formalism---has not been very successful mainly because of aprohibitive computational cost. We propose a reformulation of the NEGFtechnique in terms of the electronic wave functions of the system in anenergy--time representation. The numerical algorithm we obtain scales nowlinearly with the simulated time and the volume of the system, and makessimulation of systems with $10^5-10^6$ atoms/sites feasible. We leverage thistool to propose new intriguing effects and experiments. In particular weintroduce the concept of dynamical modification of interference pattern of aquantum system. For instance, we show that when raising a DC voltage $V$ to anelectronic interferometer, the transient current responseoscillates as $cos(eVt/hbar)$. We expect a wealth of new effects whennanoelectronic circuits are probed fast enough. The tools and conceptsdeveloped in this work shall play a key role in the analysis and proposal ofupcoming experiments
Weis, Mateusz. "Growth and spectroscopic studies (continuous and time-resolved) of ultrathin films of topological insulators". Thesis, Le Mans, 2019. http://www.theses.fr/2019LEMA1001.
Topological insulators (TI) are one of the critical elements for the new generation of electronics and spintronics devices. Such as charge-to-spin current conversion gates or Dirac fermions based nanometer scale Schottky diodes. When reduced just too a few single layers or exposed to additional doping, TI begins to show a dramatic effect that changes the electronic structure and in consequence dynamics of carriers and phonons. In order to describe those behaviors, I used advanced high-vacuum cluster with MBE to produce ultrathin films of Bi2Te3. The samples were grown on a muscovite mica substrate. The monocrystalline structure of the film was confirmed with both LEED and RHEED measurements, and the complementary studies of electronic structure focused on the analysis of the valence band and core levels. The femtosecond pump-probe spectroscopy has been used to excite the hot carriers and generate coherent optical phonons within Bi2Te3 nanostructures and observe it in the time domain.In this thesis, I reveal an evident modification of the out-of-equilibrium carriers and phonons dynamics when extreme thickness or doping modify the BT layer. Performed experimental optical measurement integrate both bulk and surface electrons, but nonnegligible surface carriers contribution still gives a strong response. This continuous and time-domain investigation provides new insight into physical properties of topological insulators and shows that downscaling the topological insulators properties and their interaction with metallic interfaces have to be taken into account for potential TIs based spintronic devices
Skilitsi, Anastasia Ioanna. "Applications of time-resolved spectroscopy for microenvironment sensing and biomolecular interactions studies". Thesis, Strasbourg, 2017. http://www.theses.fr/2017STRAE029/document.
In the context of the present thesis, UV-Vis time-resolved spectroscopy was applied targeting the photophysics investigation of different environmentally sensitive molecular systems, but also as a biosensing approach to reveal molecular interactions or structural dynamics on much slower time scales (sec to min), using droplet microfluidics triggering structural relaxation through out-of-equilibrium initial conditions. I thus investigated on a three-axis-target spanning from 1) the in-depth investigation of the emissive properties of biosensors in order to allow their quantitative use in biomolecular interaction studies, to 2) the development of an original experimental approach to enable resolving the structural relaxation kinetics of an out-of-equilibrium distribution of biomolecular structures, and finally 3) the technological application of time resolved fluorescence for precise, rapid, cost effective, biomolecular interaction assays, appealing both for academic and industrial arenas
Bhuckory, Shashi. "Quantum dots and upconverting nanoparticles : Bioconjugation and time-resolved multiplexed FRET spectroscopy for cancer diagnostics". Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLS447/document.
Combining high sensitivity with simultaneous analysis of numerous biomarkers (multiplexing) is an essential requirement for significantly improving the field of biomedical diagnostics. Such progresses would allow earlier diagnosis, which is required for numerous diseases such as cancer or cardiac diseases. FRET-immunoassays are based on biomolecular recognition events that occur between biomarkers and two specific antibodies conjugated with different fluorophores. The spatial proximity of the two fluorophores can lead to Förster resonance energy transfer (FRET), which can be detected for biomarker quantification. To date, such assays are established using lanthanide complexes as FRET donors and fluorescence dyes as FRET acceptors. However, these assays do not provide sufficient multiplexing capability due to spectral overlap, when several acceptor dyes are used. This project aims at exploiting the exceptional photophysical properties of terbium complexes (Tb) and semiconductor quantum dots (QDs) to provide ultrasensitive multiplexed FRETimmunoassays. We also studied the optical and morphological properties of novel core and core/shell upconverting nanoparticles doped with ytterbium (Yb) and erbium (Er) ions as possible FRET-donors for biosensing
Zhang, Zailan. "Electronic structures, quasi-particle and gap dynamics in copper oxides superconductors using Time and Angle Resolved Photoemission Spectroscopy". Electronic Thesis or Diss., Paris 6, 2017. https://accesdistant.sorbonne-universite.fr/login?url=https://theses-intra.sorbonne-universite.fr/2017PA066126.pdf.
The superconductors of the copper-oxide family have been matter of extensive investigations and are still subject of fierce debates. After 30 years of research, some issues have been settled, whereas others remain controversial. The evolution of the superconducting order parameter with temperature and doping level is an exemplary case. In this thesis, we report a systematic Time resolved Angle Resolved PhotoEmission Spectroscopy (ARPES) study of the optimally doped Bi2Sr2CaCu2O8+δ to explore the possibility that an intense photoexcitation of the superconductor can generate a state with incoherent copper pairs and no superfluid density. The employed experimental methods allow us to measure the dynamics of non-equilibrium electrons and of the superconducting gap, providing complementary information to conventional ARPES and optical measurement. Our time resolved ARPES data of Bi2Sr2CaCu2O8+δ, report a momentum-dependent collapse of the superconducting gap upon photoexcitation. Interestingly, the QP relaxation develops a faster component at the threshold fluence F_pair where the gap has fully collapsed. The comparison between the F_pair and the F_phase extracted by tr-THz suggested the existence a fluence regime when the Cooper pairs have survived, but without holding superfluid current. A second major challenge in the physics of HTSCs is the poor understanding of the normal phase at high temperature. We also present the ARPES study of the near nodal pseudo-gap in La2-xBaxCuO4 (LBCO) to show a possible link with charge modulation (stripes). Our data show that the near nodal gap open below the LTT-LTO transition, which is linked to the formation of such modulations, instead of the one where spin modulations appear. The data show that the band structure of LBCO is affected by a renormalization setting in prior to the 70 meV kink. We were able to correlate this renormalization of the ARPES data to the region where the Cu-O bond-stretching mode soften, both in energy and momentum space
Nĕmec, Hynek. "Time-resolved terahertz spectroscopy applied to the investigation of magnetic materials and photonic structures". Grenoble INPG, 2006. http://www.theses.fr/2006INPG0020.
Two distinct branches of optics are combined in this work: Time-domain terahertz spectroscopy, and photonic structures. The works at first provides a survey of tools utilized for exploration of the terahertz region, and it en riches them by a method for simultaneous determination of dielectric and magnetic response of materials and metamaterials. Photonic structures operating in the terahertz range form the subject of the rest of this thesis. A periodically modulated dielectric waveguide is studied theoretically using a modal method: ThE band structure of guided and leaky modes is calculated and resonant modes are described. One-dimensional photonic crystals with a defect are then investigated in detail. Formation of defect modes is analyzed theoretically in a photonic crystal with a twinning defect. The analysis makes it possible to formulate requirements on a design of a structure with defect modes tunable by external parameters. Following these guidelines, we have successfully designed, fabricated and characterized photonic crystals with thermally tunable defect modes with relative tunability reaching 60 %
Lobato, Bailón Laura. "Internal dynamics of heme-based sensor proteins studied using advanced time-resolved optical spectroscopy". Palaiseau, Ecole polytechnique, 2013. http://pastel.archives-ouvertes.fr/pastel-00866894.
Heme-proteins are involved in a large range of biological functions, including respiration, oxygen transport and xenobiotic detoxification. Importantly, bacterial heme-based sensor proteins exploit the ligation properties of heme to sense environmental gases. This thesis focuses on internal dynamics studies of the 6-coordinate heme-based gas sensor proteins CooA, from Rhodospirillum rubrum and DNR from Pseudomonas aeruginosa that are involved in adaptation of the metabolism of the organism to their environment. CooA and DNR, belonging to the important family of catabolite gene activator proteins, are transcription factors that bind DNA upon gas activation, thus enabling transcription of specific genes. Both sensor proteins are thought to undergo a large and delocalized conformational change upon binding of the physiological ligand to the heme (CO for CooA and NO for DNR). Here advanced optical spectroscopy techniques are used to investigate the mechanism and molecular pathway of activation/desactivation in this class of proteins. DNA-protein interactions were studied with steady-state and femtosecond ultrafast time resolved fluorescence techniques, using labeled DNA substrates. Physiological ligand-sensitive DNA binding in the nanomolar affinity range was deduced from anisotropy experiments. Quenching of the fluorescence label by energy transfer to the native heme in the protein moiety of the complex was observed, and the rate of this process, reflecting the heme-substrate distance, was determined directly from the measured fluorescence decays. This observation opens the perspective of mapping out the global protein conformational changes using time-resolved FRET techniques. The primary processes in heme-based sensor switching mechanisms concern ligand binding and ligand dissociation from the heme. Femtosecond transient absorption experiments were performed in order to study the ligand dynamics in CooA and DNR in the vicinity of the heme. In DNR, upon photodissociation of NO, particularly fast and efficient geminate recombination was observed. This strongly strengthens the hypothesis that NO-sensors act as ligand traps. Also, the energetic barriers involved in CO migration have been determined in both sensor proteins by temperature dependence studies. All 6-coordinate heme-based sensor proteins that function via the exchange of an internal residue and the gas molecule as a heme ligand, display barrierless recombination and a thermally activated CO-escape out of the heme pocket. By contrast, the barrier for the CO-escape appears smaller or absent for 5-coordinate systems, as has been found for the mycobacterial heme-sensor DosT. These findings point to a general mechanism, where similar protein motions are required for both, ligand exchange and ligand escape. For reasons of comparison, the energetic barriers have also been studied in ligand binding variants of the electron transfer protein cytochrome c. Here, a more complex mechanism of multiple barriers in the ligand escape pathway was deduced. This feature is proposed to reflect the rather rigid nature of this non-sensor protein, which contains a 6-coordinate heme and is devoid of ligand entry pathways in the native state. Finally, the primary processes occurring in the wild type and mutant heme domains of the recently discovered oxygen sensor YddV from Escherichia coli were investigated. In particular, an important role in the ligand dynamics was elucidated for the distal tyrosine residue. This residue hydrogen bonds to heme-bound O2 and NO molecules and was found to have a remarkably discriminating effect: after respective dissociation from the heme, it strongly promotes O2 rebinding, but favors NO escape from the heme pocket
Zhang, Zailan. "Electronic structures, quasi-particle and gap dynamics in copper oxides superconductors using Time and Angle Resolved Photoemission Spectroscopy". Thesis, Paris 6, 2017. http://www.theses.fr/2017PA066126/document.
The superconductors of the copper-oxide family have been matter of extensive investigations and are still subject of fierce debates. After 30 years of research, some issues have been settled, whereas others remain controversial. The evolution of the superconducting order parameter with temperature and doping level is an exemplary case. In this thesis, we report a systematic Time resolved Angle Resolved PhotoEmission Spectroscopy (ARPES) study of the optimally doped Bi2Sr2CaCu2O8+δ to explore the possibility that an intense photoexcitation of the superconductor can generate a state with incoherent copper pairs and no superfluid density. The employed experimental methods allow us to measure the dynamics of non-equilibrium electrons and of the superconducting gap, providing complementary information to conventional ARPES and optical measurement. Our time resolved ARPES data of Bi2Sr2CaCu2O8+δ, report a momentum-dependent collapse of the superconducting gap upon photoexcitation. Interestingly, the QP relaxation develops a faster component at the threshold fluence F_pair where the gap has fully collapsed. The comparison between the F_pair and the F_phase extracted by tr-THz suggested the existence a fluence regime when the Cooper pairs have survived, but without holding superfluid current. A second major challenge in the physics of HTSCs is the poor understanding of the normal phase at high temperature. We also present the ARPES study of the near nodal pseudo-gap in La2-xBaxCuO4 (LBCO) to show a possible link with charge modulation (stripes). Our data show that the near nodal gap open below the LTT-LTO transition, which is linked to the formation of such modulations, instead of the one where spin modulations appear. The data show that the band structure of LBCO is affected by a renormalization setting in prior to the 70 meV kink. We were able to correlate this renormalization of the ARPES data to the region where the Cu-O bond-stretching mode soften, both in energy and momentum space
Morajkar, Pranay P. "Application of laser photolysis coupled to time resolved optical detection methods to study the kinetics and spectroscopy of atmospherically relevant species". Thesis, Lille 1, 2012. http://www.theses.fr/2012LIL10063/document.
OH and HO2 radicals play a vital role in many oxidation processes in the atmosphere. Thedegradation of volatile organic compounds under tropospheric conditions is induced by reaction withhydroxyl radicals followed by the subsequent chemistry of the initial OH oxidation products with O2.This thesis deals with the kinetic study of some of these atmospherically relevant reactions to betterunderstand their oxidation mechanisms using experimental techniques such as laser photolysiscoupled to detection by Laser Induced Fluorescence (LIF, for OH), continuous wave- Cavity RingdownSpectroscopy (cw-CRDS, for HO2) and time resolved UV spectroscopy (UV, forHexamethylbenzene-OH adduct). Different chemical systems have been studied using the above techniques: 1) the reaction ofHO2 radicals with formaldehyde, 2) the 248 nm photolysis of acetaldehyde and 3) the OH initiatedoxidation of Hexamethyl benzene. In addition to this, the spectroscopic application of cw-CRDStechnique and UV spectroscopy has been used for the measurement of absorption cross section ofselected absorption lines of formaldehyde in the near infrared region and Hexamethylbenzene-OHadduct in the UV region respectively
Oher, Hanna. "A combined ab initio and time-resolved laser-induced fluorescence study of uranium-ligand interactions". Thesis, Lille 1, 2020. http://www.theses.fr/2020LIL1R032.
Uranyl complexes have been the subject of many research works for fundamental chemistry of actinides, environmental issues, or nuclear fuel cycle processes. The formation of various uranium(VI) complexes, with ligands in solution must be characterized for a better understanding of U(VI) speciation. Uranyl-ligand interactions and symmetry of the complexes both affect the electronic structure of U(VI), and thus its luminescence properties. Time-resolved laser induced fluorescence spectroscopy (TRLFS) is one of the widely used techniques to get insights on the closest chemical environment of the uranyl ion in samples, owing to its high sensitivity and selectivity. However, the luminescence spectra fingerprints hold information within and beyond the first-coordination sphere of uranyl(VI), that needs to be more deeply investigated by supplementary techniques.A promising route for data interpretation consists in creating a synergy between TRLFS and ab initio-based interpretations. Luminescence spectra of uranyl complexes in solution typically show well-spaced vibronic progressions that overlap with the pure electronic transition from the excited state to the ground state. This has driven the theoretical methodology implementation. In the frame of this thesis, time-dependent density functional theory (TD-DFT) with hybrid and range-separated functionals is used to model the electronic structure of uranium(VI) complexes. This represents an effective theoretical approach with a reasonable computational cost and accuracy, compared with computationally expensive wave-function based methods, in a relativistic context. It enabled to characterize the main spectral parameters and the first low-lying excited state of uranyl compounds with different ligands and counterions after the photo-excitation, and to compute with a high accuracy the vibronic progression in order to guide the interpretation of experimental results.In particular we focused our efforts on characterizing the influence of the organic or inorganic closest chemical environment of the uranium(VI)-based complexes. We studied 1) the influence of the extracting agent such as Aliquate 336 and solvent effect on uranyl tetrahalides; 2) inorganic Ca2+ and Mg2+ counterions on uranyl triscarbonates; and 3) monoamide ligands (di-2-ethylhexyl-isobutyramide) on uranyl binitrate complexes. Their electronic structures and main spectroscopic properties have been estimated by both TRLFS and ab initio techniques. The theoretical approach enabled to calculate the main luminescence emissions of the complexes with the corresponding assignment of the electronic transitions and vibronic modes involved. For all the studied complexes, a good agreement between theory and experiment was found, allowing to build a full picture about the capabilities of the methods
Schmid, Marco. "Conformational dynamics of G-quadruplex DNA probed by time-resolved circular dichroism". Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLX107/document.
Guanine-quadruplexes (G4) are non-canonical DNA structures that result from the hydrophobic stacking of guanine quartets stabilized by metal cations (typically Na+ and K+). There is now an increasing body of experimental evidence of their occurrence in important cell functions correlated to their folding/unfolding mechanisms. However, only few studies have addressed the dynamical aspect of their formation. In this context, we have undertaken the study of several intramolecular G4 with a novel extension of temperature-jump experiments capable to measure the thermal denaturation and the consecutive renaturation of DNA over a time window spanning a few ten milliseconds to seconds. Conformational changes have been monitored by time-resolved circular dichroism (CD), which is known to be sensitive to the chiral arrangement of guanines in the G4 scaffolds.Prior to time-resolved measurements, within the frame of a collaboration with DISCO/SOLEIL, we have performed static synchrotron radiation CD measurements on several short G4-forming sequences, such as human telomere, thrombin-binding aptamer and c-MYC promoter sequences, displaying distinct topologies. Denaturation and renaturation kinetics are found to exhibit biphasic decays with time constants of a few hundred milliseconds and a few seconds, respectively. Those kinetics depend strongly on the amplitude of the temperature jump and the concentration of cations. Taken together these observations suggest the existence of multiple folding pathways on extremely rugged landscapes
Villamil, Franco Carolina. "Ultrafast dynamics of excitons and charge carriers in colloidal perovskite nanostructures studied by time-resolved optical spectroscopies". Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPASF012.
Halide perovskites have emerged as very promising photoactive materials due to their outstanding optoelectronic properties combined with low-cost processability. In spite of their successful implementation in photovoltaic or light-emitting devices, a deep understanding of the dynamics of relaxation and recombination is still missing in order to enhance the device performances. This thesis focuses on the study of two major fundamental processes occurring in colloidal halide perovskite nanostructures: the hot charge carrier/exciton relaxation (“cooling”), after excitation above the optical bandgap, and the non-radiative Auger recombination, taking place after high-fluence or high-photon energy excitation. In particular, time-resolved photoluminescence and femtosecond transient absorption spectroscopy were used to investigate the confinement and composition effects in strongly confined two-dimensional (2D) lead iodide perovskite nanoplatelets (NPLs), that were synthesized following the development and optimizations of colloidal methods. For the investigation of the cooling dynamics, a global analysis method based on single value decomposition was used, where the temporal evolution of the spectral lineshapes was modeled with a sequential kinetic scheme. This method was succesfully applied to effectively describe the continuous energy relaxation in weakly-confined thick FAPbI₃ nanoplates (FA=formamidinium) and allowed disantangleting the hot phonon bottleneck from the Auger reheating effects at high excitation fluence. Furthermore, the global analysis was essential to investigate the cooling dynamics in strongly confined 2D NPLs presenting large Stark effects and discrete excitonic band-edge transition far away from the continuum of states (exciton binding energy in several hundreds of meV). As in the weakly confined samples, the cooling rate of the NPLs decreases with the excitation fluence. However, it is faster in more-strongly confined samples, evidencing the absence of an intrinsic phonon bottleneck. Furthermore, the cooling rate and its evolution with the exciton density were found independent of the nature of the internal cations (FA, MA=methylammonium and Cs=cesium). However, when comparing with the rate measured in 2D layered perovskite thin film with equivalent quantum well thickness, the results strongly suggest a role of the surface ligands in the possibility to release the excess energy to the surrounding environment. This ligand-mediated relaxation mechanism becomes dominent in the thinner NPL samples with enhanced exciton/ligand vibrational mode coupling. Then, the multiple exciton recombination dominated by non-radiative Auger recombination (AR) was studied in the strongly-confined 2D perovskite NPLs. Due to the large asymmetric geometry and the limited exciton wavefunction delocalization, the AR rate strongly depends on the exciton density via the initial average inter-exciton distance. At low fluence, this distance is in several tens of nanometers such as the AR is limited by the exciton diffusion in the 2D plane. It thus occurs on a timescale of several hundreds of picoseconds and depends on the sample dimensionality (thickness and lateral sizes). In contrast, high excitation fluences produce “overlapping” excitons with inter-exciton distances of only a few times the exciton Bohr radius, resulting in AR times of less than 10 ps and independent of the NPL composition nor geometry. Finally, the exciton population dynamics of 2D NPLs after excitation in the ultraviolet was measured. The strong dependence of the AR with the inter-exciton distance allows the identification of multiple exciton generation (MEG), which involves the reaction of “geminate biexcitons” produced by the absorption of a single high-energy photon
Staedter, David. "Femtosecond time-resolved spectroscopy in polyatomic systems investigated by velocity-map imaging and high-order harmonic generation". Toulouse 3, 2013. http://thesesups.ups-tlse.fr/2116/.
Revealing the underlying ultrafast dynamics in molecular reaction spectroscopy demands state-of-the-art imaging techniques to follow a molecular process step by step. Femtosecond time-resolved velocity-map imaging is used to study the photodissociation dynamics of chlorine azide (ClN3). Here especially the co-fragments chlorine and N3 are studied on the femtosecond timescale in two excitation energy regions around 4. 67 eV and 6. 12 eV, leading to the formation of a linear N3 fragment and a cyclic N3 fragment, respectively. This work is the first femtosecond spectroscopy study revealing the formation of cyclic N3. Tetrathiafulvalene (TTF, C6H4S4) electronic relaxation is studied, while scanning the electronic excitation around 4 eV, by time resolved mass and photoelectron spectroscopy. As only few is known about the ion continuum about TTF the imaging photoelectron photoion coincidence (iPEPICO) technique is used in order to disentangle the complex ionic dissociation. The second part of the thesis is based on the generation and application of XUV light pulses by high-order harmonic generation with an intense femtosecond laser pulse in a molecular target. Two types of phase sensitive attosecond spectroscopy experiments were conducted to study the vibrational dynamics of SF6: one using strong field transient grating spectroscopy, where high-order harmonic generation takes place in a grating of excitation, and the second experiment using high-order harmonic interferometry using two intense XUV probe pulses. The temporal dependencies in phase and amplitude reveal the vibrational dynamics in SF6 and demonstrate that high-order harmonic generation is sensitive to the internal excitations. Last but not least, the use of high-order harmonics as a XUV photon source for the velocity-map imaging spectrometer is investigated. Using time-resolved photoelectron imaging, the relaxation dynamics initiated with 15. 5 eV in argon and 9. 3 eV in acetylene are revealed
Hérissan, Alexandre. "Étude par Time Resolved Microwave Conductivity de photocatalyseurs pour la dépollution de l’eau". Thesis, Université Paris-Saclay (ComUE), 2015. http://www.theses.fr/2015SACLS097/document.
The photocatalysis is based on the excitation of semiconductor by photons with an energy superior or equal to the gap, generating electron-hole pairs. These are very reactive and able to react at the interface, involving for exemple the total oxidation of an organic compound. This method can be used on wastewater to eliminate the organic pollutants. With a view to use the sun as a light source this method may become an economical and ecological way for the water treatment. Light interaction between light and semiconductor and the charge-carrier dynamics are fundamental processes for photocatalysis and it is necessary to understand them in order to manage with this process and develop more efficient materials. The Time Resolved Microwave Conductivity (TRMC) is a method based on the reflexion of microwaves on an excited semiconductor which is linked to the number of photo-generated charge-carriers. This method allows us to probe in real time the charge-carrier dynamics in semiconductor. This work is included in the ANR Photonorm project. It consists in a TRMC study on titanium dioxyde TiO2 used for water depollution by photocatalysis. One part of this study consists in the characterization of the opto-electronic properties of materials for which the charge-carrier dynamics will be compared with the photocatalytic activity. The beneficial effect of nanoparticles deposition of gold, silver or gold-copper bimetallics on commercial TiO2 will be linked to the observation of free electrons observed by TRMC . The beneficial effect on photocatalysis in visible light was linked to an electron injection in TiO2 by bismuth nanoparticles. The second part of this work consists in a more fundamental study of charge-carrier dynamics on commercial or synthetized for the Photonorm project. I will be shown the importance of excitation wavelength and intensities on charge carrier generation. The importance of surface effect and environment will be emphasized by several ways. The first one just consist in surface treatment which can have a major importance on charge-carrier dynamics and photocatalysis, probably in connection with the presence or not of impurities on the surface. The second way consists in impregnating TiO2 by organic dyes which show a strong visible light absorption. The TRMC measurements highlight the interaction between the adsorbed molecules and the semiconducteur, including the electron injection from the excited dye to the TiO2 but also an increased recombination effect. The third method consist in modified the working atmosphere in TRMC. The major role of oxygen is so observed on charge-carrier dynamics, with an effect of electron capture, involving in photocatalytic mechanism.Finally TRMC proves to be a convenient method for studying charge-carrier dynamics in semiconductors, which allow a better understanding of fundamental processes bound to photocatalysis
Chan, Alan Jenkin. "3D Time-Resolved Hetero-Coagulation of Soft Latex and Hard Colloidal Particles and the Structuration of the Resulting Gel Network". Thesis, Université Paris-Saclay (ComUE), 2015. http://www.theses.fr/2015SACLS026.
Natural rubber (NR) is an indispensable raw material used in the manufacturing of more than 40,000 products primarily due to its excellent intrinsic physical properties. However, NR is seldom used in its raw state. Often, it needs to be reinforced with particulate fillers (nanoparticles) to further improve its physical strength required for most applications. The precise origin of this mechanical reinforcement effect remains unclear, however, optimal reinforcements appears to depend on the dispersion of filler in the NR matrix and the interaction of NR and filler.It was found that the conventional method of pouring fine powders in a solid block of rubber/melt is not the most efficient way to disperse the fillers. The new alternative approach in which the two components are first dispersed in liquid has shown promising results but available literature is still very limited. Furthermore, the microscopic mechanism involved in the interaction of NR and filler in liquid is still unknown. In this context, we (i) described the physico-chemical surface properties of NR particles in liquid, (ii) identified key filler (size, composition, surface activity, concentration) and solution (ion valence) related parameters to comprehend the structural, morphological, and dynamical evolution of the NR-filler interaction, and (iii) quantified the mechanical properties of the NR particles. With this approach we were able to provide the first reports on the physical processes involved in the interaction of NR and filler. More importantly, a recipe for the basic yet crucial parameters that controls and modulates NR-filler heteroaggregation was established. This could open the way to further understand the reinforcement effect
Pierucci, Debora. "The electronic structure and reactivity of tri-coordinated silicon atoms on water-covered Si(001)surface : time-resolved XPS and STM studies". Paris 6, 2013. http://www.theses.fr/2013PA066557.
Ce travail de thèse porte sur les propriétés électroniques des liaisons pendantes d’atomes de silicium isolés, présents sur la surface de silicium Si(001)-2×1 après saturation par des molécules d’eau à température ambiante. Ces défauts sont tri-coordonnés Si-SiH/Si-SiOH et peuvent être comparés à ceux produits par la désorption d’atomes d’hydrogène, Si-SiH,par une pointe STM sur la surface Si(001)-2×1 hydrogénée. Ces derniers ont dernièrement attirés l’attention en raison de leurs possibles utilisations comme point de départ pour des réactions radicalaires. Quant aux défauts présents sur la surface recouverte d’eau, ils sont semblables à ceux observés à l’interface Si(001)/SiO2, et peuvent s’avérer cruciaux dans un domaine comme la microélectronique. Les liaisons pendantes à la surface (H,OH)-Si(001)-2×1sont amphotères et représentent une densité de ~0. 01 ML. En effet, elles peuvent être chargées positivement, négativement ou bien être quasi-neutres en fonction du dopage du substrat. En raison de la présence de ces défauts de charge sur la surface, les bandes, dans le semi-conducteur, se courbent. Cette courbure de bande peut être simplement mesurée par spectroscopie de photoémission (XPS) en utilisant le rayonnement synchrotron et peut, ensuite, être convertie en une densité de charge de surface, en utilisant les modèles de la physique classique. L’innovation de ce travail de thèse réside dans la combinaison d’une technique d’analyse comme la spectroscopie de photoélectron des rayons X (XPS) sondant l’intégralité de la surface avec une technique d’analyse locale comme la microscopie à effet tunnel (STM). De plus, ce type d’étude est impossible avec la surface hydrogénée puisque les liaisons pendantes doivent être produites une à une par une pointe STM, alors qu’elles sont naturellement présente sur la surface saturée en eau. Cette étude est d’autant plus originale qu’elle utilise la spectroscopie de photoémission ‘en temps réel’ et ‘résolue en temps’. En effet, la spectroscopie dépendante en temps englobe deux différents aspects. Un aspect ‘temps réel’ qui est utilisé pour suivre la cinétique de réactions chimiques, à une échelle de temps de la dizaine de secondes, comme par exemple la saturation de la surface Si(001)-2×1 par des molécules d’eau. Et un aspect ‘résolu en temps’ qui consiste à suivre la réponse de la surface à une excitation par un pulse laser (pompe: pulse laser dans le visible de ~fs) en utilisant le rayonnement synchrotron (sonde, résolution limitée par la durée du pulse synchrotron de ~50 ps). La thèse est construite en trois parties de la façon suivante: nous avons tout d’abord étudié l’adsorption d’eau sur la surface propre de Si(001)-2×1 par photoémission en ‘temps réel’. Une étude cinétique de l’absorption d’eau par la surface Si(001)-2×1 propre a été réalisée pour différentes pressions d’eau dans la chambre d’analyse (P = 5x10-10 mbar, P = 1x10-9 mbar, P = 1x10-8 mbar). Ces mesures ont permis d’établir que le mécanisme d’absorption ne suivait pas une cinétique de type Langmuir mais de type Kisliuk. Dans ce modèle, la molécule d’eau est d’abord piégée en tant que précurseur, et diffuse rapidement sur la surface jusqu’à trouver un site adapté à la chimisorption. Le dopage du substrat ne semble avoir aucun impact sur cette cinétique. La photoémission a aussi permis de déterminer la densité surfacique en oxygène, les variations de la courbure de bandes ainsi que le travail de sortie du matériau et d’en déduire la position du niveau de Fermi à la surface ainsi que le diagramme de bande de la surface de silicium saturée d’eau en fonction du dopage du substrat. En parallèle, nous avons analysé en détail la topographie de cette surface ainsi que la structure électronique des liaisons pendantes isolées (en particulier leur état de charge) par STM. Grace à une très bonne résolution, il a été possible de distinguer les fragments OH et H sur la surface et leur répartition sur les différents dimères de silicium. La quantité exacte de liaison pendante en fonction du dopage a aussi pu être calculée. La maximum de liaison pendantes a été observé pour l’échantillon hautement dopé n. Nous avons, ensuite, sélectionné deux molécules organiques: un alcène, le styrène et un aldéhyde, le benzaldéhyde, dans le but de tester la réactivité de ces liaisons pendantes. Nous avons réalisé une étude où se combinent mesures STM, photoémission (XPS), absorption des rayons X (NEXAFS) ainsi que des mesures de spectroscopie de perte d’énergie d’électron a haute résolution (HREELS) associée à des calculs DFT de modes vibrationnels. Pour surface recouverte d’eau, comme c’est souvent le cas, le problème de la réactivité des liaisons pendantes c’est avéré plus complexe que prévu et plus nuancé en comparaison aux résultats obtenus pour la surface hydrogénée. En effet ces deux molécules réagissent sur la surface hydrogénée par réaction en chaine à partir d’un atome de silicium radicalaire de la surface. Dans le cas de la surface recouverte d’eau, la réaction en chaine n’est pas observée. Le désordre chimique de cette surface (terminaisons Si-H et Si-OH) semble empêcher la propagation radicalaire; l’intermédiaire réactionnel radicalaire est piégé dans un minimum d’énergie, il est nécessaire de franchir une importante barrière de potentiel pour pouvoir capturer un hydrogène voisin d’un groupement Si-OH ou bien Si-H. Finalement, les propriétés de la surface (H,OH)-Si(001)-2×1 (densité surfacique de charge, courbure de bande, caractérisation de defaults chargés) en fonction du dopage étant bien comprises, nous avons réalisé des expériences de photoémission ‘résolue en temps’ dans le but de suivre la dynamique liée au photovoltage de surface. En raison de la ressemblance entre les liaisons pendantes de la surface (H,OH)-Si(001)-2×1 avec le défauts Pb de l’interface silicium-oxyde de silicium, cette interface a aussi été étudiée dans le but de permettre des comparaisons. Cette expérience consiste à perturber la distribution de charge de la surface (en injectant de la charge dans la couche de charge d’espace) dans le but d’obtenir l’échelle de temps du retour à l’équilibre. L’injection de charge est réalisée à partir d’un laser femto λ = 800 nm. Les paires d’électrons-trous crées sont séparée par le champ électrique présent dans la couche de charges d’espace. Une accumulation des porteurs de charges dans la zone proche de la surface crée un potentiel référencé comme photovoltage de surface (SPV) qui diminue la courbure de bande à la surface du semi-conducteur. L’équilibre est restauré par le transport de porteurs de charges depuis le volume vers la surface par émission thermoïonique. L’évolution du phénomène peut être suivi en sondant la surface par le rayonnement synchrotron qui permet la détermination du déplacement de l’énergie de liaison du niveau de cœur Si 2p du silicium et ainsi l’obtention du profil temporel du photovoltage de surface
Rouxel, Jérémy. "A rigorous multipolar framework for nanoparticles optical properties description : theory and experiments". Thesis, Troyes, 2015. http://www.theses.fr/2015TROY0013/document.
Using metallic nanoparticles with a threefold symmetry thorough the study, the impact of the symmetry on the nonlinear properties is investigated. Interpretations of polarization-resolved SHG experiments indicate the importance of multipolar resonances, in particular quadrupole and octupole, to explain the strong values of the nonlinear susceptibilities in such systems. A fully irreducible formalism is then developed to treat extended objects like nanoparticles. In this formalism, the nonlinear response tensor is a discrete set of values easily constrained by symmetries instead of a field. This formalism permits to describe simply linear and nonlinear optical response from nanoparticles. Finally, time-domain experiments are conducted with the aim to connect spatial and spectral properties. These experiments allow to interpret the spectra in terms of eigenmodes
Wu, Yu-Tang. "Förster Resonance Energy Transfer Immunoassays Using Engineered Proteins for Breast Cancer Biomarker Detection". Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLS340/document.
Engineered affinity proteins have raised great interest due to their extremely small size compared to full length antibodies. Such small binding proteins have demonstrated many advantages such as quick biodistribution, good penetration into tumor tissue, and fast elimination from serum and nondiseased tissues. Thus, they are expected to be excellent alternatives to antibodies for clinical applications. This thesis focuses on the development of biosensors based on engineered antibodies and time-resolved Förster resonance energy transfer (FRET) through biological recognition of biomarkers. FRET-based immunoassays are established using terbium complexes (Tb) as FRET donors and semiconductor quantum dots (QDs) as FRET acceptors. The exceptional photophysical properties of the Tb-QD FRET pair allow for ultrasensitive quantitative biosensing. Single-domain antibodies (sdAb) and small engineered scaffold antibodies (ADAPT) are used to investigate different antibody-conjugation strategies for quantifying human epidermal growth factor receptors (EGFR, HER2) as clinical biomarkers. This work can be considered as a prerequisite to implementing QDs into applied clinical diagnostics
Ould, Metidji Mahmoud. "Nanodispersion et développement de traceurs fluorescents". Thesis, Lyon, 2016. http://www.theses.fr/2016LYSE1188/document.
The dispersion of inorganic materials in organic and aqueous media is a decisive factor for their industrial implementation. These materials are used in many areas from the oil industry to polishing. Herein, we focus on studying the stability of these materials in different media such as: (i) the aqueous solvents used for the formulation of abrasive slurries, (ii) the waters of oil operations and (iii) crude oil and its derivatives. Our objective is to improve the luminescence properties of these materials for the oil industry and the abrasive properties for polishing applications.We have developed stable formulations of lanthanide complexes (Ln) derived from DOTA and nanoparticles (NPs) of zinc sulfide doped with manganese for water-management in oil fields. These materials were characterized by time-resolved fluorescence (TRF) to solve the problems associated with the auto-fluorescence of petroleum products in the operating water.Furthermore, we studied the dispersion of specific compounds in different fuels in order to develop new anti-counterfeiting markers for crude oil and its derivatives. Finally, we tried to improve the dispersion of diamond nanoparticles in aqueous media in order to enhance the efficiency of diamond abrasive suspensions based for polishing sapphire a-plan
Xu, Jingyue. "Sensitive and mutiplexed microRNA quantification using amplified time-gated Förster resonance energy transfer". Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPASS137.
As new generation of biomarkers, microRNAs are associated with many cancers and diseases, which has led to a great demand for developing clinical miRNA diagnostic methods. Isothermal amplification technologies, such as rolling circle amplification and catalytic hairpin assembly, have emerged as powerful methods for highly rapid, specific and sensitive microRNA assays. This thesis focuses on developing microRNA biosensors based on isothermal amplification technologies and time-resolved Förster resonance energy transfer from lanthanide complexes to organic dyes or quantum dots. The proposed amplified microRNA biosensors have very low limits of detections, and are applied to human clinical samples, successfully revealing the relevance for cancer diagnostics. As simultaneous detection of multiple microRNAs is highly demanded, temporal multiplexed detection of microRNAs is also realized based on distinguishable excited-state lifetimes of Tb complexes and dyes. Moreover, the amplified microRNA nanosensor based on Tb-to-quantum dots FRET demonstrated the possibility of spectral multiplexed detection of microRNAs with high sensitivity and selectivity
Fotso, Gueutue Eric Stéphane. "Spectroscopie Raman résolue en temps pour les hautes températures". Thesis, Orléans, 2018. http://www.theses.fr/2018ORLE2023/document.
This work presents the optimization of a time-resolved Raman spectroscopy device dedicated to very high temperatures. This device meets the ever-increasing need to study in real time phase transformations and reaction kinetics in extreme environments. This device has been validated under working conditions on oxides (Gd₂O3, Y₂O3, ZrO₂ , ZrSiO4 et CeO₂) and nitrides (h-BN). The potentialities of the device have enabled the main technological and instrumental locks that limit the use of high temperature Raman spectroscopy to be removed. The three main highlights illustrating the innovative nature of this work are as follows. The first corresponds to the new world record for high temperature Raman analysis through the acquisition of the E₂g mode of h-BN up to 2700°C.A comparison of the performance of the two Pockels and ICCD channels shows that the Pockels channel is more efficient than the ICCD, but more difficult to implement. The second important fact concerns the other applications of time-resolved Raman, as to separate the contribution of Raman scattering and luminescence. The last application presents the study of the comparative time dependence of resonant and non-resonant Raman scattering. The resonant Raman is triggered systematically before the non-resonant. More generally, the interest of time-resolved Raman methods opens new fields of application in the characterization of materials in extreme conditions, possibly in situ: aeronautics, refractories, steel industry, nuclear, etc
Nilforoushan, Niloufar. "Out-of-equilibrium electron dynamics of Dirac semimetals and strongly correlated materials". Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLS573/document.
Quantum materials is a new term in condensed matter physics that unifies all materials in which strong electronic correlation governs physical properties of the system (e.g. Mott insulators) and materials whose electronic properties are determined by the geometry of the electronic wave function (e.g. Dirac materials). These materials show emergent properties– that is, properties that only appear by intricate interactions among many degrees of freedom, such as charge, spin and orbital, giving rise to topological properties of electrons. The study of these interactions and competitions between the relevant degrees of freedom demands applying ultrafast pump-probe techniques. Particularly, femtosecond laser pulses act only on the electrons and set them to an out-of-equilibrium state inexplicable by the Fermi-Dirac distribution. The ensuing dynamics involves various processes and the rate at which the relaxation occurs is related to the coupling constants. Moreover, in time-resolved pump-probe techniques light can act as an additional external parameter to change of the phase diagram – different from thermodynamic parameters. It gives us the opportunity of stabilizing new states inaccessible by quasi-adiabatic thermal pathways or eventually manipulating the physical properties of the systems.In this thesis, we performed different experiments in order to study the equilibrium and out-of-equilibrium properties of two correlated compounds: BaCo₁₋ₓNiₓS₂ and (V₁₋ₓMₓ)₂O₃.The first part of the project was mainly devoted to the study of BaNiS₂ that is the metallic precursor of the Mott transition in BaCo₁₋ₓNiₓS₂. By applying ARPES, we studied the electronic band structure of BaNiS₂ in its entire Brillouin zone. These results combined with some theoretical calculations give evidence of a novel correlation-induced and two-dimensional Dirac cone with d-orbital character. The band crossing is protected by the specific symmetries of the crystal structure. We also investigated the electronic band structure of the Mott insulator BaCoS₂ in its magnetic and nonmagnetic phases.In the second part, we studied the out-of-equilibrium electron dynamics of BaNiS₂ and (V₁₋ₓMx)₂O₃. By means of tr-ARPES and tr-reflectivity measurements, we observed an ultrafast and non-thermal renormalization of the Dirac cone in BaNiS₂ . This phenomenon is purely provoked by the electronic excitation and is stabilized by the interplay between the electrons and phonons. Moreover, by applying various pump-probe techniques (XFEL-based tr-XRD and tr-Reflectivity) we also explored the out-of-equilibrium phases of the prototype Mott-Hubbard material (V₁₋ₓMx)₂O₃ in different parts of its phase diagram. Our results show a transient non-thermal phase developing immediately after ultrafast photoexcitation and lasting few picoseconds in both metallic and insulating phases. This transient phase is followed by a structural distortion that corresponds to a lattice hardening and is marked by a “blue shift” of the A₁g phonon mode. These results underline the importance of the orbital filling as well as the strong effect of the selective electron-lattice coupling in the strongly correlated materials
Bascoul, Guillaume. "Applications de la cartographie en émission de lumière dynamique (Time Resolved Imaging) pour l’analyse de défaillance des composants VLSI". Thesis, Bordeaux 1, 2013. http://www.theses.fr/2013BOR14876/document.
VLSI ("Very Large Scale Integration") technologies are part of our daily lives and our miniaturization needs are increasing. The densification of transistors not only means trouble locating the so-called "hard defects" occurring during the development phases (debug) or aging, but also the appearance of pure non-functional behaviors related to component design flaws. Techniques discussed in this document are intended to probe the microelectronic circuits using a tool called dynamic light emission (Time Resolved Imaging - TRI) in search of abnormal behavior in terms of timings and patterns involved in structures. To go further, this instrument also allows viewing thermographic time resolved thermal transients within a component
Ekvall, Karin. "Time resolved laser spectroscopy". Doctoral thesis, KTH, Physics, 2000. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3063.
Moore, B. D. "Time-resolved infrared spectroscopy". Thesis, University of Nottingham, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.332449.
De, Anda Villa Manuel. "Dynamique structurelle induite par laser ultrabref sondée par spectroscopie des photoélectrons résolue en temps". Thesis, Sorbonne université, 2019. http://www.theses.fr/2019SORUS193.
This work aims to study the lattice structural dynamics of metals under laser femtosecond excitation using time-resolved photoelectron spectroscopy (Tr-PES). When irradiated by short infrared laser pulses, the thermal out-of-equilibrium state established between hot electrons and a cold lattice rises specific dynamics where the thermodynamic properties of matter are still subject to debate. The theoretical description of highly excited materials is difficult and appeals new experimental results to improve the understanding of these physical processes and material properties. Nonetheless, important challenges arise from the use of Tr-PES. When metals are irradiated with strong femtosecond infrared laser pulses, non-linear effects, like multiphoton ionization, can take place and produce photoelectrons with tenths of eV of kinetic energy. This pump photoelectron background can conceal the probe-induced photoelectron spectrum, and perturb the probe spectrum via Coulomb interactions (called space-charge effect). To overcome these challenges three actions were carried out. We designed and built a 100 eV beamline to avoid the superposition between the pump background and the probe photoelectron spectrum. The pump/probe space-charge effect was extensively studied theoretically and experimentally. Finally, the pump photoemission was greatly reduced in our experiments by carefully tuning the experimental parameters. This led us to perform Tr-PES measurements on copper samples of the lattice structural dynamics following the evolution of the photoelectron spectrum. The experiment constituted a proof-of-principle of the Tr-PES technique to study materials under strong excitation
Derom, Stephane. "Plasmonic cavities and optical nanosources". Thesis, Dijon, 2013. http://www.theses.fr/2013DIJOS060/document.
Optical microcavities exhibit high resonance quality, so that, they are of key interest for the design of low-threshold lasers or for achieving strong coupling regime. But, such systems support modes whose the volume remain diffraction limited.In this manuscript, we are interested in their plasmonic counterparts because they support confined modes at the sub-wavelength scale. First, we study an in-plane plasmonic cavity which is the transposition of 1D optical cavity to surface wave. We characterize the cavity by measuring the fluorescence lifetime of dye molecules deposited inside.Then, we are interested in 3-dimension mode confinement achieved by spherical metal nanoparticles. We discuss on the definition of the mode volume used in cavity quantum electrodynamic and based on the calculation of energy confinement around the particle. We also simulate the fluorescence enhancement of rare-earth ions embedded inside core-shell plasmonic particles. Finally, we disturb the photodynamic emission of a single-photon source by puttingthe extremity of a plasmonic tip nearby the emitter
Hua, Ying. "Structures auto-assemblées de guanines étudiées par spectroscopie optique résolue en temps". Phd thesis, Université Paris Sud - Paris XI, 2013. http://tel.archives-ouvertes.fr/tel-00873695.
Zhuang, Bo. "Fundamental Processes in Flavoprotein Photochemistry". Thesis, Institut polytechnique de Paris, 2022. https://tel.archives-ouvertes.fr/tel-03789651.
Flavins are derivatives of vitamin B2 that form a highly versatile group of chromophores found in a large variety of enzymes and photoreceptor proteins. They can adopt three different redox states with various protonation states, leading to at least five physiologically relevant forms, with distinct electronic absorption spectra. Despite the diverse photophysical properties of the flavin cofactors, there are only very few natural photo-responsive flavoproteins. The vast majority of flavoproteins perform non-light-driven physiological functions (“non-photoactive”), although ultrafast, reversible photoinduced redox reactions between flavins and surrounding residues still widely occur in these systems, which can be viewed as photo-protective “self-quenching”. The past few decades have seen a blooming in the study of flavoproteins for their photocatalytic and photo-biotechnological applications. Moreover, a newly emerging approach in the development of novel photocatalysts from canonical “non-photoactive” flavoenzymes is making use of the photochemistry of reduced flavins instead of the oxidized resting state. Furthermore, practical implications of photochemistry of yet different flavin species are envisaged, but a basic understanding of their mechanisms is still required. In this thesis, applying ultrafast absorption and fluorescence spectroscopy combined with molecular simulations and quantum chemistry approaches, a variety of fundamental photochemical processes in flavoproteins is investigated. First the photoreduction of oxidized flavins was revisited in a flavoprotein, ferredoxin-NADP+ oxidoreductase (FNR), with closely packed reactant configurations, allowing ultrafast formation of intermediate radical pairs. Combining experimental and modeling techniques allowed a detailed assessment of the influence of the environment on the spectral properties of both the anionic flavin and the cationic amino acid (tyrosine or tryptophan) radicals. We further investigated the photochemistry of protein-bound flavin species in different chemical states that are largely unexplored in the literature. It is demonstrated that photooxidation of anionic flavin radicals, which act as reaction intermediates in many biochemical reactions, efficiently occurs within ~100 fs in several flavoprotein oxidases. This process, effectively the reverse of the well-known photoreduction of oxidized flavin may constitute a universal decay pathway. The excited-state properties of fully reduced flavins were studied in several FNR systems where they are involved as functional intermediates, and compared with those in solution. Valuable information concerning their electronic structures and the flavin flexibility was obtained and compared with atomic simulations, with important catalytic implications. Finally, an unprecedented photo-dissociation phenomenon was revealed for a non-covalent charge transfer complex of flavin and a inhibitor in the flavoenzyme monomeric sarcosine oxidase. This process occurs on the timescale of a few hundred femtoseconds and can be attributed to a well-defined photoinduced isomerization of the inhibitor. Altogether, the described findings, which include the discovery of two hitherto undocumented photochemical processes in flavoproteins, expand the repertoire of photochemistry involving flavin cofactors. This work may open new avenues for the exploration of flavin photochemistry with ultimately possible practical implications as novel photocatalysts and optogenetic tools
Snow, Paul Alistair. "Time-resolved spectroscopy of GaSb". Thesis, University of Oxford, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.308681.
Legrand, Marie. "Advanced imaging of transient and spectral luminescence for optoelectronic characterization of photovoltaic materials". Electronic Thesis or Diss., Sorbonne université, 2023. https://accesdistant.sorbonne-universite.fr/login?url=https://theses-intra.sorbonne-universite.fr/2023SORUS066.pdf.
Photoluminescence characterization of photovoltaic absorbers provides the charge transport phenomena and the optoelectronic properties on which their performance relies. However, their obtention is based on physical models and may require uncontrolled assumptions and unknown parameters. This thesis explores how acquiring spectrally resolved maps of photoluminescence in pulsed excitation can contribute to material characterization while limiting the necessary prior knowledge and controlling underlying hypotheses and models. On the one hand, we developed imaging systems describing the emitted intensity in four dimensions: 2D spatial, temporal and spectral. On the other hand, we performed excitation wavelength variation studies and investigated their relationship with light absorption. Maps of intensity can be acquired by pixelated detectors or non-imaging detectors, as in Single-pixel imaging. This approach employs spatial light modulation to reconstruct images and is particularly relevant to obtain multidimensional images. It is thus of interest for photoluminescence as each dimension brings information, as demonstrated by the setups already in use. A hyperspectral imager, providing the spectrum in each pixel, allows the characterization of material properties and the charge carriers generated. Complementarily, time-resolved imaging gives an insight into the transport mechanisms. We review and propose different techniques to obtain 4D data corresponding to the temporal evolution of the spectrum in each pixel of an image I_PL (x,y,energy,time). It provides the correlation between temporal and spectral dimensions, which was not available in the lab previously. Three measurement approaches were developed based on the principle of single-pixel imaging. They correspond to different sampling schemes in the 4D space, focusing on temporal and spectral dimensions that are reached with high resolutions. Their implementation was challenging as photoluminescence corresponds to low light conditions, and the higher the resolutions, the lower the sensitivity. Each dimension of light involved must be accurately reconstructed while entangled in the acquisition process. Particularly, the impact of diffraction and interferences due to the spatial light modulator has been investigated. This instrumental work allowed, first of all, combined time and spectrally resolved imaging (2x3D) of perovskite. It allowed monitoring of light-induced mechanisms that modify the photoluminescence spectrum and dynamics. Secondly, it has led to the characterization in 4D of the emission of a gallium arsenide wafer. The joint evolution of the signal in temporal, spatial, and spectral dimensions is observed due to band-filling and diffusion. At last, a workflow based on pixel clustering algorithms is proposed. A spatial map is obtained by single-pixel imaging, from which areas of interest are determined before the decay is obtained with high temporal and spectral resolutions. It allows an original sampling of photoluminescence with a high signal-to-noise ratio enabling its application to various samples and injection conditions. These last two approaches are unique to the best of our knowledge and provide photoluminescence variation in the combined spatial, temporal, and spectral domains. In addition, we have set up a methodology to perform excitation wavelength studies on the hyperspectral imager. It was demonstrated on an inhomogeneous perovskite sample from which the local relative absorptivity is obtained on a wide spectral range by combined analysis of the emission and excitation spectra. Reflectivity measurements completing this study provide optical and topological information allowing us to refine the interpretation of photoluminescence maps
Camus, Enrique Castro. "Polarisation resolved terahertz time domain spectroscopy". Thesis, University of Oxford, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.441048.
Hess, Stefan. "Time-resolved spectroscopy of gallium nitride". Thesis, University of Oxford, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.301575.
Ghose, Avisek. "Etude des propriétés photophysiques de dérivés de l’oxyluciférine et leurs applications à l’étude d’interactions entre biomolécules". Thesis, Strasbourg, 2015. http://www.theses.fr/2015STRAJ005/document.
In this work, we investigated the emission mechanism of the optically active part of the firefly luciferin-luciferase complex. This bioluminescent system is widely used in bioanalytical assay. This amazing natural phenomenon results in the emission of visible light (yellow-green-red) from the photoproduct Oxyluciferin. This color tuning mechanism involves six chemical species, but their active involvement in the excited state proton transfer (ESPT) mechanism was poorly understood so far. One of the main finding presented here relies on the identification of six chemical forms of Oxyluciferin involved in the color tuning fluorescence emission mechanism. This result was obtained by studying the optical properties of different structural analogues of firefly Oxyluciferin in aqueous buffer. Different spectroscopic (steady state and time-resolved) and chemometric approaches have been applied to reveal the emission mechanism. In addition, the photophysical properties of Oxyluciferin in complex with the Luciferase enzyme Luciola cruciata have been studied in aqueous buffer as well. In parallel, derivatives displaying environment sensitive emission were used to monitor biomolecular interactions. In particular, we demonstrated that Oxyluciferin can be employed to map intracellular pH by using fluorescence microscopy within living cells. With the help of another Oxyluciferin derivative we were able to monitor the interaction between a HIV-1 protein and different oligonucleotide sequences by means of ratiometric measurements. Finally we develop an approach based on cysteine labeling to monitor in vitro protein-protein interaction
Murphy, Thomas S. "Time-resolved spectroscopic studies of reactive intermediates". Thesis, University of Nottingham, 2016. http://eprints.nottingham.ac.uk/31288/.
Amin, Chalhoub Eliane. "Etude des processus thermophysiques en régime d'interaction laser/matière nanoseconde par pyro/réflectométrie rapide". Thesis, Orléans, 2010. http://www.theses.fr/2010ORLE2081/document.
The recent development of nanotechnology has made the study and the characterisation of thermal properties of thin films and nanomaterials very important for the development and the quality of new technologies. Our experimental setup is designed and built in order to study different phenomena, in real time, that arise while the interaction of a laser with materials at the nanosecond scale. This system is composed of two complementary optical diagnostics, the time resolved reflectivity and the fast infrared pyrometry. First, we have shown the ability to study in real time the surface structural changes in the case of a thin metal layer deposited on an insulating substrate, the phenomenon of photoluminescence and the kinetics of melting/resolidification and also the ablation. In addition, we present a novel method in order to determine the thermal properties (volumetric heat capacity and thermal conductivity) of nanostructured surfaces. The analysis is based on the use of a proven theoretical model that is adjusted with an optimisation algorithm on our experimental measurements
Bregy, Harald. "Time-resolved infrared spectroscopy of photoswitchable thioxopeptides /". [S.l.] : [s.n.], 2009. http://opac.nebis.ch/cgi-bin/showAbstract.pl?sys=000286596.
Moore, John Neville. "Time resolved spectroscopy of water-soluble anthraquinones". Thesis, Imperial College London, 1986. http://hdl.handle.net/10044/1/38109.
Dunkelberger, Adam David. "Time-resolved electronic spectroscopy of 2,2'-bisindene". Connect to resource, 2007. http://hdl.handle.net/1811/28440.
Title from first page of PDF file. Document formatted into pages: contains 35 p.; also includes graphics. Includes bibliographical references (p.35). Available online via Ohio State University's Knowledge Bank.
Tatham, Martin Christopher. "Time resolved Raman spectroscopy of semiconductor structures". Thesis, University of Oxford, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.305429.
Grills, David C. "Time-resolved infrared spectroscopy in Supercritical fluids". Thesis, University of Nottingham, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.285677.
Clark, Ian P. "Time-resolved infrared spectroscopy of organometallic states". Thesis, University of Nottingham, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.363942.
Khajeh, Maryam. "Kinetic measurements using time-resolved NMR spectroscopy". Thesis, University of Manchester, 2010. https://www.research.manchester.ac.uk/portal/en/theses/kinetic-measurements-using-timeresolved-nmr-spectroscopy(aae85bb3-de19-450a-96ab-50e2dfd89da7).html.
Brown, Alan Jeffrey. "Time resolved evanescent wave induced fluorescence spectroscopy". Thesis, Imperial College London, 1990. http://hdl.handle.net/10044/1/47790.
George, Michael W. "Time-resolved infrared spectroscopy of reaction intermediates". Thesis, University of Nottingham, 1990. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.591102.
Sjöberg, Béatrice. "Oxydation des protéines par les espèces réactives de l'oxygène : l'importance de l'environnement protéique". Phd thesis, Université de Franche-Comté, 2013. http://tel.archives-ouvertes.fr/tel-01024104.
Calladine, James Andrew. "Time-resolved infrared spectroscopic studies of reaction intermediates". Thesis, University of Nottingham, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.537693.
Cowan, Alexander J. "Time-resolved infrared spectroscopic studies of reaction mechanisms". Thesis, University of Nottingham, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.444615.
Durantel, Florent. "Mesure de luminescence induite par faisceaux d'ions lourds rapides résolue à l'echelle picoseconde". Thesis, Normandie, 2018. http://www.theses.fr/2018NORMC261/document.
We developed an instrument for measuring the luminescence induced by a heavy ion beam (nucleons 12) and energy in the range of MeV / nucleon. Based on a single photon counting method obtained by coincidences, the device can provide in the same run a 16-channel energy spectrum in the UV-visible- IR region (185-920 nm) and a time-resolved response in the range of ns up to µs for each channel. Temperature measurements can be performed from room temperature down to 30K.This work places particular emphasis on data extraction methods: Once the need to deconvolve the signals demonstrated the evaluation of different instrument profiles (simulated and reconstructed from measurements) leads to a systematic temporal characterization of each component of the device. Then, these instrumental profiles are used in two deconvolution methods: least squares first followed by maximum entropy method.Two typical materials are tested: the Strontium Titanate for the study of the dynamics of the electronic excitation, and a commercial scintillator, the BC400, for the study of the aging and the decrease of performances with fluence. In both cases, we have been able to highlight the presence of an ultrafast component of subnanosecond time constant